<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<input type="text" id = "i1">
<input type="text" id = "i2"><br>
<input type="button" value="加" onclick="f(1)">
<input type="button" value="减" onclick="f(2)">
<input type="button" value="乘" onclick="f(3)">
<input type="button" value="除" onclick="f(4)">
<div>结果:</div>
<script>
    let i1 = document.querySelector("#i1");
    let i2 = document.querySelector("#i2");
    let d = document.querySelector("div");
    function f(x) {
        if(isNaN(i1.value)||isNaN(i2.value)){
            d.innerText = "输入错误!"
            return;
        }
        switch (x) {
            case 1:d.innerText = "结果:"+(parseFloat(i1.value)+parseFloat(i2.value));
            break;
            case 2:d.innerText = "结果:"+(i1.value-i2.value);
            break;
            case 3:d.innerText = "结果:"+i1.value*i2.value;
            break;
            case 4:d.innerText = "结果:"+i1.value/i2.value;
            break;
        }

    }



</script>

</body>
</html>